In my copending United States Patent Application Ser. No. 906,151 filed May 16, 1978 and entitled TENSION MEASURING DEVICE, there is disclosed a tensiometer so designed as to be attachable to a rope or cable or any equivalent line such as might be used in a derrick, hoist, crane or similar structure without requiring access to the ends of the line. In other words, the tensiometer can be attached without having to disassemble the line from the particular apparatus involved. For convenience in terminology, the rope, cable or line involved will hereafter simply be referred to as a cable, it being understood that any equivalent line, chain, rope or the like could be substituted.
Another of my tensiometers is shown and described in U.S. Pat. No. 4,163,126 issued July 31, 1979 wherein again the device is so designed as to enable attachment thereof to a cable without need of access to the ends of the cable. The tensiometer in this latter patent is for purposes of indicating only when a given load has been exceeded, rather than making a continuous measurement of tension in a line.
While enormous advantages accrue from providing such tensiometers wherein the same can be attached without having access to the ends of the cable, so that it is not necessary to restring cable structures, there is still required a slackening of the cable portion to which the tensiometer is to be attached in order to enable the attachment operation to be carried out. In other words, if the cable is under a heavy load or high tension, it is not possible to attach tensiometers of the type under consideration without requiring some type of auxiliary crane or hoist which will relieve the tension in the cable while attaching the tensiometer. The reason is that the cable must deviate from a straight line in passing under a first guide pulley, over the center pulley and thence under the second guide pulley so that a lateral force is generated against the center guide pulley constituting a function of the load on the cable. A person simply is not strong enough to deflect the cable manually in an attempt to attach the tensiometer device when the load is of any appreciable magnitude.